Sprag clutch

[Kenif]

Just thought I'd share some new found wisdom with you.

My lovely new (to me) Mille was in the workshop for a bit of a spruce. Full service, new discs, MPL cylinder etc.
All was done, mechanic tried to start bike and scrunch!
Yep, the sprag clutch went

Anyway short version is, found a cheaper replacement than the Aprilia version. Proper stuff is:

OEM Aprilia Sprag Housing - 0659123
OEM Aprilia Sprag Clutch - 0659110
OEM Aprilia Sprag Gear - 0634595
Aprilia Stator Cover Gasket - 0650340_GS

BUT, you can save £75 by getting the Ducati alternative sprag clutch, product code 70140071A . Managed to get one (£100, from stock, unbelievable!) from Metropolis in Vauxhall but other dealers quoted 4-5 days (days, NOT months) for the part

Hope nobody ever needs it but the truth is now out there if you have need.

[D-Rider]

Yep it's a fact - we had this one as a "Sticky" on the old ARS (posted by Pierre)

http://www.jahlis.net/ars/viewtopic.php ... ade28a1f05

Thanks for reminding us though.
Think I'll move this to the Aprilia Technical section and restore its "stickyness"

[Kenif]

Yep, I used Pierre's advice on 'why you shouldn't use a blowtorch' to warn the garage!

[yellowasp]

ust remind me of what you shold do to prevent this, being a new user and all

[D-Rider]

Basically, avoid strying to start it with a weak battery or excessive resistance in the starter motor circuit (caused by dirty contacts, contacts not tight in the path between battery and starter motor ..... or with a starter relay whose switching contacts are oxidising).

The starter motor needs enough power to spin up quickly and engage the sprag effectively.

[Pierre]

Busy so quick post to say since I did that post the engines done about 20 trackdays with no problems, probably about 35000miles on the engine now ( 3000 on the revlimiter ) and have only taken it out to put a factory engine in Will be using it in a future project though as it still runs sweet as a nut

[Kenif]

It works!!!

Picked the bike up today, started sweet as a nut first time, with no scrunchy noises

Quick ride through 10 miles of crappy traffic and am happy again. Stuck it on charge when I got home (you know how often garages start up your bike when they're playing) and the battery was nearly dead. No WAY would that have started before the new sprag clutch went in!

Er, and the new battery, starter relay and iridium plugs...

oh, the MPL clutch slave cylinder was a bit of treat to!

Big thanks to Pierre for always informing us of new and unique ways to keep an Aprilia running and to Spoonz (other site) for loads of helpful stuff

[blinkey501]

I have just done the sprag clutch on tims bike.
I found an easy method in being able to lock the flywheel whilst undoing the centre bolt rather than removing the clutch cover on a previous sprag I changed.
I would like to point out the boring stuff....... I do not accept responsibility if you try this and by an act of god something go's wrong....
Remove the oil tank after it is fully drained.

Remove the stator cover

This shows you the flats on the flywheel

Spanner attached. You can use the crash bungs to assist in removal if you have bungs fitted. Have someone hold the bike whilst pushing down on the bar.
Make sure the spanner is a good fit onto the flats of the flywheel to prevent slipping.

Washer removed. And bolt fitted back up to the flywheel and backed off a couple of turns.

You can now fit a two or three leg puller onto the flywheel. With the centre of the puller pressing onto the centre bolt.
The bolt stops damage to the internal threads of the crank.
The pressure on the puller does not have to be too great.
Heat evenly with a blow torch around the centre of the flywheel until the locktite on the flywheel/crank breaks the seal.
Remove the centre bolt and the flywheel can be removed wearing suitable heat resistant gloves.


NOTE. I used this method as I had a three leg puller. An aprilia type puller can be purchased if you want to buy one.

[blinkey501]

The three allen bolts you see in the picture near the outer of the inner ring hold your sprag clutch in place.
These should be removed after the flywheel has been removed.


When re assembling use the correct locktite for the flywheel/crank.
Obtain the correct torque settings for the three allen bolts and the flywheel centre bolts.
I could give you the settings but I don't want to make fitting a sprag too easy for you

[fatboy]

Good info, brill pics, nice one Blinkey !

[D-Rider]

Nice work Jay

[mangocrazy]

Good stuff, Jay. I hope I never have to use the info, but it's good to know it's there if ever it's needed.

[Kwackerz]

Sprag clutch..? Pfft.. "One has a man who does that for one.."



Great stuff Jay!

[blinkey501]

How it works
http://www.youtube.com/watch?v=Fsp3fm4K ... pp=desktop

[blinkey501]

I have been reading on AF1 about the recommended internal puller that is used for removing the stator flywheel.
It would seem that there is cheaper copies of the Aprilia puller on the market.
The problems with these pullers seems to be that the metal they are made from is substandard with the threads stripping, leaving the puller stuck in the stator.
This is the method used by a member on AF1 having to use to remove the puller.

You have been warned!!!!!!!